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P1631 — Immobilizer incorrect challenge response
Universal diagnostic code. Below: what it means, common causes, symptoms, and the exact bench-programming fix path.
Common causes
- •Donor cluster/ECU installed
- •Failed pairing attempt
- •EEPROM corruption
Symptoms you'll see
- •Crank-no-start
- •IMMO warning
- •Key fob locks/unlocks but won't start
The fix path
Brand-specific bench services to re-pair OR bypass: BMW EWS Delete, VW/Audi IMMO Delete, Mercedes EIS Cloning.
AML services that fix this
Mail in the affected module, we bench-program, ship back next business day. Flat pricing, return shipping included.
VW/Audi MED17/ME17 IMMO Delete + VIN
$250Permanently remove immobilizer coding from MED17/ME17 ECUs. Optional VIN correction.
Service detailsMercedes EIS Cloning (Pre-2014)
$250Clone a working Mercedes EIS to a replacement EIS — keeps your existing keys.
Service detailsBMW DME EWS Delete (MS41/42/43/45, MSS50-70)
$150Plug-and-play EWS delete for BMW M52/M54/S54/S62/S65 DMEs. Ship your DME, get it back IMMO-off and ready to start.
Service detailsRelated diagnostic codes
Not sure which service applies?
Text us your year/make/model + which scanner caught the code — we'll tell you exactly which module to ship and which service to pick.